Generally, two types of sensors (for example, piezo-electric type sensors and magnerostriction type sensors) are being mainly used as ultrasonic sensors.
The piezo-electric type sensors denote sensors in which a voltage is induced by applying a pressure to an object such as a quartz crystal, a piezo-electric material (for example, PZT), or a piezo-electric polymer, but a vibration is caused by applying a voltage to the object. The magnerostriction type sensors denote sensors that use the joule effect (in which a vibration is caused by applying a magnetic field) and the villari effect (in which a magnetic field is generated by applying a stress) which are shown in an alloy of iron, nickel, and cobalt.
The ultrasonic sensors use an element, having the piezo-electric characteristic and the magnerostriction characteristic, as a vibration source. Fast vibrations equal to the number of frequencies are caused by applying high-frequency electric energy to a ceramic element, in which case when the applied frequency is 20 KHz or higher, the ceramic element generates an inaudible ultrasonic wave having a specific frequency band according to the vibrations.
Especially, sensors using a piezo-electric element sense an object by using an ultrasonic wave generated by the piezo-electric element, and specifically, the sensors intermittently transmit an ultrasonic pulse signal to receive a reflected wave from a nearby obstacle, thereby sensing the object.
The ultrasonic sensor is used for back sonars and corner sonars of vehicles and parking spot sensors that detect whether there is a space between a corresponding vehicle and an obstacle such as a side wall in column parking.
The ultrasonic sensor, as illustrated in FIG. 1, includes a case 110 that accommodates various components, a piezo-electric element 20 that is accommodated in the case 10, a printed circuit board (PCB) 30, a lead wire 40 that is connected to the piezo-electric element 20 at one end of the lead wire 40 and connected to the PCB 30 at the other end, a sound absorbing material 50 that maintains a constant attenuation of a vibration of the case 10, and a charging material 60 that seals the inside of the case 10.
In the case 10, the piezo-electric element 20 is disposed at and adhered to a bottom of the case 10, one of the lead wire 40 is connected to the case 10, and the sound-absorbing material 50 is assembled on the piezo-electric element 20.
In this state, when the sound-absorbing material 50 directly contacts the piezo-electric element 20, the sound-absorbing material 50 can affect a vibration characteristic of the piezo-electric element 20, and the case 10 has a structure in which the piezo-electric element 20 is separated from the sound-absorbing material 50.
Therefore, in order to separate the piezo-electric element 20 and the sound-absorbing material 50, the charging material 60 is coated and hardened near the piezo-electric element 20 to form a mounting part 70 having a height higher than the piezo-electric element 20, and the sound-absorbing material 50 is assembled to the mounting part 70.
Here, a connection path to the PCB 30 is provided by connecting the lead wire 40 and a connection component 80, and the charging material 60 or the like is charged into the case 10.
The connection path to the PCB 30 has a case in which the lead wire 40 and a connector 90 are applied and a case in which a pin type is provided.
The lead wire 40 has a type in which the connector 90 is connected to a distal end of each of a power line and a ground line. However, since an automation process for the lead wire 40 is impossible, the lead wire 40 is provided to have a length longer than a real connection distance in consideration of a manual process.
In the pin type, a power pin and a ground pin are provided in plurality, the pins may be directly connected to the PCB 30.
In this case, each of the pins is provided at an accurate position. To this end, a component or a structure for fixing each of the pins is needed.
However, when external power is applied to the case 10 itself and other components, a vibration characteristic can be affected by the external power.
Therefore, the case 10 has an anti-vibration structure in which external power or a vibration applied to the pins is not transferred to the case 10 and the other components.
As described above, since a structure of the sensor assembly is complicated and an overall process for the sensor assembly is performed manually, it is difficult to accurately assemble a sensor.
Particularly, when connecting the PCB 30 to the connection component 80 for the lead wire 40, it is impossible to align the lead wire 40 and maintain an alignment state of the lead wire 40, and thus, a manual process of connecting the lead wire 40 and the PCB 30 is inevitably performed.
In addition, in an ultrasonic wave transceiver including the case 10, the piezo-electric element 20, the lead wire 40, and the sound-absorbing material 50, since a process of coating and hardening the charging material 60 for providing the mounting part 70 with the sound-absorbing material 50 disposed therein is repeatedly performed, many processes are performed, causing an increase in manufacturing cost.